Various organic synthesis reactions using transition metal complexes as a catalyst have hitherto been developed and utilized for many purposes. In particular, there are a number of reports on asymmetric catalysts to be used in asymmetric syntheses, i.e., asymmetric isomerization, asymmetric hydrogenation, and the like. Of the reported asymmetric catalysts, metal complexes formed between metallic rhodium and an optically active tertiary phosphine are especially well known as catalysts for asymmetric hydrogenation. Such complexes typically include a rhodium-phosphine complex using 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as BINAP) as a ligand as disclosed in JP-A-55-61937 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). Further, Inoue et al. report in Chemistry Letters, pp. 1007-1008 (1985) that citronellol can be obtained in an optical yield of 66% by asymmetric hydrogenation of geraniol or nerol using various rhodium-phosphine complexes.
On the other hand, known ruthenium complexes, though there are not so many reports as compared with rhodium complexes, include those having BINAP or 2,2'-bis(di-p-tolylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as T-BINAP) as a ligand, e.g., Ru.sub.2 Cl.sub.4 (BINAP).sub.2 NEt.sub.3 (wherein Et represents an ethyl group, hereinafter the same) and Ru.sub.2 Cl.sub.4 (T-BINAP).sub.2 NEt.sub.3 as reported in Ikariya et al., J. Chem. Soc. Chem. Commun., p. 922 (1985), Ru(O.sub.2 CR).sub.2 (BINAP) and Ru(O.sub.2 CR).sub.2 (T-BINAP) (wherein R represents a lower alkyl group, a lower alkyl-substituted phenyl group, etc.) as disclosed in JP-A-62-265293, and [RuH.sub.80 (R-BINAP).sub.m ]X.sub.n (wherein R represents a hydrogen atom or a methyl group; X represents ClO.sub.4, BF.sub.4 or PF.sub.6 ; when .lambda. is 0, then m is 1, and n is 2; and when .lambda. is 1, then m is 2, n is 1) as disclosed in JP-A-63-41487.
However, these conventional ruthenium complexes require complicated processes for the preparation thereof or the yields and stability of the preparation have not been satisfactory. Besides, the catalytic activity as well as duration of the activity of these complexes are still insufficient.
Although metallic rhodium provides excellent complex catalysts, it is expensive due to limitations in place and quantity of production When used as a catalyst component, it forms a large proportion in cost of the catalyst, ultimately resulting in an increase in cost of the final commercial products While metallic ruthenium is cheaper than metallic rhodium and appears promising as a catalyst component for advantageous industrial application, it still has problems in achievement of precise reactions and its range of application. Therefore, it has been keenly demanded to develop a catalyst which can be prepared easily at low cost, has high activity and durability, and catalyzes asymmetric reactions to attain high optical yields, i.e., to produce reaction products having high optical purity.